Solution blending Grafting

Simple blends often exhibit poor mechanical properties and unstable morphologies. A solution consists in the compatibilization of such blends. Graft or block copolymers are added to the blends in order to act as compatibilizers. 

Kim et al. (66) used poly(3-hexylthiophene) (P3HT)-graft-PMMA as a compatibilizer to prepare MWCNT-PMMA composites by solution blending. The CNT content was varied from 0.01 to 0.1 wt%. The resulting composites showed improved tensile strength and modulus. 

Unexpectedly, when films were cast from these poly (vinyl chloride-g-2-ethylhexyl acrylate/acrylonitrile) solutions, they were crystal clear with very low haze values. Table IV lists some of the physical properties of these poly (vinyl chloride-g-2-ethylhexyl acrylate/acrylonitrile) cast films values for a solution blend of the acrylic copolymer and PVC are also included. While tensile strengths of the 1.0/1.5 and 1.0/4.0 acrylic copolymer/PVC-graft/blend films were about 80-90% that of the homopolymer PVC film, they were significantly higher than that of the blend polymer. Furthermore, the crescent tear strengths were higher than those of the blend and the PVC film. Most importantly, the haze values of the graft blend films were much improved over that of the blend polymer, and they more nearly approached that of the homopolymer PVC. 

Schematic representation of the morphology of PP/organoclay nanocomposites prepared by (a) ammonium ion-terminated PP and MMT-Na+, (b) static annealing of functionalized PP (e.g., with MA) and M2(Ci8)2 organoclay, (c) solution blending with simultaneous grafting of the imsaturated surfactant onto the PP chains.

Another example of solvent-assisted nanocomposite preparation involving modification of the PP chains to enhance their interaction with the clay smface is offered by the paper of Wu et al. [57]. These autiiors grafted hexamethylenediamine (HMDA) onto PP- -MA (with 0.485wt% MA) according to tire reaction below, carried out in xylene solution at 120°C for 2h, and used the product (PP-g-HMA) to prepare the nanocomposites by solution blending. PP-g-HMA was repeatedly washed with deionized water and dried under vacuum at 100°C for 12h. 

LLDPE-g-(t-butylmethacrylate)/epoxy triazine-capped PPE Melt or solution blended/selective solvent extraction/also used t-butylallylcarbamate in place of t-butyhnethacrylate, both grafted to LLDPE in the melt in presence of RI Campbell 1990... 

Shen et al. [130] prepared maleic anhydride grafted polypropylene (PP)/ expanded graphite nanocomposites by solution blending. The conductive performance of PP was improved significantly. 

The BST powder was added into the PS matrix by solution blending. The modified BST powder was added after the PS resin was dissolved in tetrahydrofuran solvent. The obtained suspension mixture was stirred for 2 h by means of ultrasonic oscillation at 20°C. The nanocomposites were prepared after removing solvent completely. An SEM micrograph of the nanocomposite is shown in Fig. 7 because of the good compatibility between bare Bao sSro sTiOs and PS matrix, few pores were observed. Furthermore, the PS-grafted Bao sSro.sTiOs show good distribution in the PS matrix. 

Methods of Blend Preparation. Most polymer pairs are immiscible, and therefore, their blends are not formed spontaneously. Moreover, the phase structure of polymer blends is not equilibrium and depends on the process of their preparation. Five different methods are used for the preparation of polymer blends (60,61) melt mixing, solution blending, latex mixing, partial block or graft copolymerization, and preparation of interpenetrating polymer networks. It should be mentioned that due to high viscosity of polymer melts, one of these methods is required for size reduction of the components (to the order of /ttm), even for miscible blends. 

A butadiene-modified clay was prepared to produce PS, HIPS, ABS terpolymer, PMMA, polypropylene, and polyethylene nanocomposites by melt- or solution blending [73, 74]. The butadiene surfactant was obtained from the reaction of vinylbenzyl chloride-grafted polybutadiene with a tertiary amine (Table 3.6). All the composites were immiscible microcomposites. 

Park et al. [20] reported on the synthesis of poly-(chloroprene-co-isobutyl methacrylate) and its compati-bilizing effect in immiscible polychloroprene-poly(iso-butyl methacrylate) blends. A copolymer of chloroprene rubber (CR) and isobutyl methacrylate (iBMA) poly[CP-Co-(BMA)] and a graft copolymer of iBMA and poly-chloroprene [poly(CR-g-iBMA)] were prepared for comparison. Blends of CR and PiBMA are prepared by the solution casting technique using THF as the solvent. The morphology and glass-transition temperature behavior indicated that the blend is an immiscible one. It was found that both the copolymers can improve the miscibility, but the efficiency is higher in poly(CR-Co-iBMA) than in poly(CR-g-iBMA),... 

With a history of more than 25 years, the free radical-induced grafting of MAH onto polyolefin substrates is one of the most studied polyolefin modification processes.29 "29, 302 The process has been carried out in the melt phase, in various forms of extruders and batch mixers, and there are numerous patents covering various aspects of the process. It has also been carried out successfully in solution and in the solid state. The materials have a range of applications including their use as precursors to graft copolymers, either directly, or during the preparation of blends.297... 

Reactive compatibilization can also be accomplished by co-vulcanization at the interface of the component particles resulting in obliteration of phase boundary. For example, when cA-polybutadiene is blended with SBR (23.5% styrene), the two glass transition temperatures merge into one after vulcanization. Co-vulcanization may take place in two steps, namely generation of a block or graft copolymer during vulcanization at the phase interface and compatibilization of the components by thickening of the interface. However, this can only happen if the temperature of co-vulcanization is above the order-disorder transition and is between the upper and lower critical solution temperature (LCST) of the blend [20]. 

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